A Johns Hopkins infectious disease expert is calling for all sexually active American women age 40 and older to get tested for the parasite Trichomonas vaginalis after new study evidence found that the sexually transmitted disease (STD) is more than twice as common in this age group than previously thought. Screening is especially important because in many cases there are no symptoms.

"We usually think of STDs as more prevalent in young people, but our study results clearly show that with trichomonas, while too many young people have it, even more, older women are infected," says senior study investigator Charlotte Gaydos, M.S., Dr.P.H.

Results of a study to be presented July 12 at the annual meeting of the International Society for STD Research, in Quebec City, Canada, by Gaydos and her co-investigators show that among 7,593 U.S. women between the ages of 18 and 89, women 50 and older had the highest trichomonas infection rate, at 13 percent. Women in their 40s were next, at 11 percent. The study, which collected test samples from women in 28 states, is believed to be the largest and most in-depth analysis of the STD ever performed in the United States, complementing periodic national surveys of adolescents and individual city reports.

"Trichomonas infections are quite treatable with antibiotics," says Gaydos, a professor at the Johns Hopkins University School of Medicine." And these high numbers really warrant older women getting screened by their family physicians and gynecologists during routine check-ups to make sure they are not infected and are not inadvertently spreading it to others."

Overall, the survey results showed that 8.7 percent of all women tested positive for the STD. Previous estimates, using older, less reliable tests had indicated an overall infection rate of less than 4 percent. In the new study, the infection rate was 8.5 percent in women ages 18 and 19, dropping slightly to 8.3 percent for women in their 20s.

Gaydos says testing is needed to prevent transmission of the parasite because some infected women and most infected men show no signs of the disease, such as liquid discharge from the vagina or penis, irritation while urinating and genital itching. Left untreated, trichomoniasis can lead to severe health problems. Trichomonas infection is closely tied to co-infection with HIV, easing transmission of the virus that causes AIDS. Gaydos says trichomoniasis can also lead to inflammation of the vagina, urethra and cervix and to pelvic inflammatory disease, and in pregnant women, the infection has been known to cause premature labor and result in more low-birth-weight babies.

The public health threat of trichomonas is compounded, Gaydos adds, by the fact that, unlike other common STDs, such as the bacteria Chlamydia trachomatis and Neisseria gonorrhoeae, confirmed cases of parasitic trichomonas infection do not have to be reported to local public health officials and the U.S. Centers for Disease Control and Prevention.

"What we are really witnessing with trichomonas, especially in older women, is that no one ever looked, no one ever tested and diagnosed, and no one is really getting treated, so the infection persists year after year," says Gaydos. She says that in addition to encouraging women to get tested, federal agencies should make trichomonas a reportable condition, as are chlamydia and gonorrhea, so that public health officials can screen, track and develop better methods to halt infections.

Among the study's other key findings were that infection rates were highest among black women of all ages, at 20 percent, almost twice what earlier estimates had suggested and more than three times the rate in whites, at 5.7 percent. Gaydos says this finding mirrors results of other health surveys tying increased STD infection rates  such as chlamydia and gonorrhea, too -- to high levels of poverty, unemployment, and lack of education in different racial and ethnic groups.

Such social and economic disparities, she says, also help explain why the infection rate in jails, in which a large proportion of the prison population is African American, was 22.3 percent; and why women in the relatively poorer Southeast United States have the highest regional trichomonas infection rate, at 14.4 percent, whereas women in the more affluent Northeast had the lowest, at 4.3 percent.

The Johns Hopkins team last December published survey results about trichomonas infection rates in men, in whom the disease is even harder to detect. Initial study data from 500 men tested for all three common STDs showed that at least 10 percent of all men participating in the study carried the parasite, whose infection can cause inflammation of the male reproductive organs. Solving the problem in men is also important, Gaydos says, because of the risk of re-infection and instances in which women and men have multiple sex partners and all will need treatment.

In the current study, test samples were collected from women in private clinics, emergency departments, hospitals, jails and community health STD clinics between July 1 and Dec. 30, 2010. Left over samples  consisting of either a urine, cervical or vaginal swab, or liquid pap smears, with the names removed  were then retested specifically for trichomonas, after they had already been clinically tested for chlamydia and gonorrhea. Researchers used the latest genetic assay, a test that is almost 100 percent foolproof in detecting trichomonas, instead of traditional testing methods, which are only accurate about half the time.

Funding for the study was provided by participating academic centers, including the Johns Hopkins University. Testing supplies were provided free of charge to testing sites by the assay equipment manufacturer, Gen-Probe, of San Diego. Gaydos has in the past received grant funding from Gen-Probe, but only for studies on the accuracy of their trichomonas assay, not this latest study.

The U.S. CDC lists Trichomonas vaginalis as the most common sexually transmitted disease in the nation, with an estimated 7.2 million men and women newly infected each year. The World Health Organization estimates the annual rate of new infected people at 173 million.

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